Engine

Engine with CVT and outstanding lubricating oil chamber

Field of the Invention

The present invention relates to an engine with a continuously variable transmission of the V-belt type (CVT) on one side in the direction of the crankcase of the engine crankcase that is suitable for use, for example, on motorcycles, and said motorcycle .

Technical background

Some of the engines for use in motorcycles, for example, are provided with a CVT of the V-belt type located on the axially outer side of the engine crankcase and including a drive pulley mounted at one end of the crankshaft, a driven pulley mounted at one end of a drive shaft placed parallel to the crankshaft, and a V-belt placed around both pulleys.

A conventional engine with said CVT type is described for example in Japanese Patent Publication No. 3095024 constituted so that part of the engine housing is defined as a transmission case to which one end of the crankshaft and one end of the Transmission shaft extends in a cantilever shape, and its distal ends are provided with the drive pulley and pulley moved around which a V-belt passes.

Another arrangement described in Japanese Patent Publication No. 2002-021989 is constituted so that the transmission case is formed separately from the engine housing, the front end portions of the crankshaft and the transmission shaft are supported through bearings with the transmission case, and air is introduced into the transmission case.

An example of a V-belt described in Japanese Patent Publication No. Hei 07-027180 has a surface, which will be in contact with the driven and driven pulleys, made of a resin element.

Another example described in Japanese Patent No. Hei 05-068398 is arranged so that the lubricating oil chamber formed in the engine housing is bulged so that it is positioned below the CVT of the V-belt type.

EP-A-1 170 480 describes the features of the preamble of claim 1.

When the CVT of the V-belt type is located on the side of the engine crankcase, the temperature in the transmission case is likely to increase due to engine heat and heat generated by friction of the V-belt. The V-belt in particular deteriorates with the thermal effect and its insufficient durability is a problem.

Therefore, the engine with the CVT of the V-belt type in the side portion of the engine requires such an arrangement that it can prevent the temperature in the transmission case from rising, prevent the V-belt from deteriorating due to the increase in temperature, and prolong the durability of the V-belt.

The object of the present invention carried out in view of the prior art situations described above is to provide a motor that can prevent the temperature in the transmission case from rising, prevent the V-belt from deteriorating prematurely due to the temperature increase, and prolong the durability of the V-belt, and provide a vehicle, such as a motorcycle, that has such an improved engine.

Said objective is achieved with the characteristics of claims 1 and 9.

Preferred embodiments are set forth in other secondary claims.

The "engine crankcase" in the sense that it is used here is a general term including the following cases: the crankcase in which the crankshaft is placed, the clutch housing in which the clutch mechanism is housed, and the crankcase of generator in which the generator is placed. Each crankcase is partially or completely formed so that it is integral with another crankcase or crankcases, or formed separately.

By the way, the term "lubricating oil" chamber in the sense that it is used here refers to the area in which lubricating oil is collected, and includes, for example, the oil collecting tray to which the lubricating oil falls and in the one collected, and the oil filter located on the distribution side of an oil pump to collect and filter lubricating oil.

Brief description of the drawings

Figure 1 is a left side view of the motorcycle on which an engine is mounted according to an embodiment of the

present invention Figure 2 is a sectional plan view that extends along line II-II in Figure 6 of the motor previous.

Figure 3 is a sectional plan view of the CVT mechanism and the clutch mechanism portion anterior motor centrifuge. Figure 4 is a right side view of the previous engine.

Figure 5 is a left side view of the previous engine. Figure 6 is a right side view of the anterior engine with the CVT mechanism and the clutch mechanism centrifugal removed.

Figure 7 is a right side view of the crankcase of the previous engine. Figure 8 is a rear sectional view along line VIII-VIII in Figure 5 of the previous crankcase. Figure 9 is a sectional view of the starter mechanism of the previous engine as seen along the line

IX-IX in Figure 5. Figure 10 is a sectional view of the previous starting mechanism. Figure 11 is a rear sectional view showing the route of lubricating oil of the previous engine. Figure 12 is a sectional view of the anterior centrifugal clutch. Figure 13 is a side view of the anterior centrifugal clutch. Figure 14 is an enlarged sectional view of an essential part of the anterior centrifugal clutch. Figure 15 is an enlarged sectional view of an essential part of the anterior centrifugal clutch. Figure 16 is a sectional view of the conventional general purpose driven pulley. Figure 17 is a sectional plan view of an engine as the second embodiment of the invention. Figure 18 is a rear sectional view of the motor of the second previous embodiment. Figure 19 is a right side view of the motor of the second previous embodiment.

Best way to put the invention into practice

The embodiments of the present invention will be described below with reference to the accompanying drawings.

Figures 1 to 15 describe a motorcycle engine as an embodiment of the present invention. Figure 1 is a left side view of a motorcycle in which an engine is mounted as an embodiment of the present invention. Figure 2 is a sectional plan view along line II-II in Figure 6 depicting the extended state of the previous engine. Figure 3 is a sectional plan view of the CVT mechanism and the centrifugal clutch mechanism portion of the anterior motor. Figures 4 and 5 are right and left side views of the engine. Figure 6 is a right side view of the anterior motor with the CVT mechanism and the centrifugal clutch mechanism removed. Figure 7 is a right side view of the crankcase of the previous engine. Figure 8 is a rear sectional view along line VIII-VIII in Figure 5 of the previous crankcase. Figure 9 is a sectional view of the starting mechanism of the previous engine as seen along the line IX-IX in Figure 5. Figure 10 is a plan view in section around the starter axis. Figure 11 is a rear sectional view of the lubricating oil path of the previous engine. Figures 12 and 13 are a sectional view and a side view of the anterior centrifugal clutch mechanism. Figures 14 and 15 are enlarged sectional views of an essential part of the anterior centrifugal clutch. By the way, the terms "right" and "left" in the sense that they are used here are understood as the motorist sitting in the seat looks.

To describe in general terms the constitution of a motorcycle 1 represented in the drawings, an engine 2 of this embodiment is mounted on the motorcycle 1, a front tube 3 is fixed to the front end of a vehicle body frame 1a to support a fork front 5 that is capable of turning right and left around its axle and that supports a front wheel 4 with an axle, a rear arm support 6 fixed to the central part of the vehicle frame 1a to support a rear arm 8 that supports a rear wheel 7 with an axis for tilting up and down, and a seat 9 formed by a front biker seat 9a and a rear biker seat 9b is mounted on the vehicle body frame 1a.

The vehicle body frame 1a is formed by right and left down tubes 1b extending from the front tube 3 obliquely back and down, upper right and left tubes 1c extending from the rear ends of the down tubes 1b obliquely back and up, and right and left seat rails 1d extending in the longitudinal direction of the vehicle to interconnect the descending tubes 1b and the upper tubes 1c. The vehicle body frame 1a is surrounded with a resin vehicle body cover 10 formed by a front cover 10a, a leg protector 10b, and a side cover 10c.

A steering handlebar 11 is fixed to the upper end of the front fork 5 and surrounded with a handlebar cover 11a. A rear shock absorber 12 is suspended between the rear arm 8 and the rear arm support 6.

The engine 2 is a four-cylinder, air-cooled, single-cylinder engine, suspended between rear lower parts of the downcomers 1b, with its cylinder axis tilted forward approximately 45 degrees. The motor 2 includes a motor unit 15, a CVT of the V-belt type 16, a multi-layer centrifugal clutch mechanism of wet type 17, and a reduction gear mechanism 18.

The engine unit 15, in a general description, is constituted by a cylinder block 19, a cylinder head 20 placed on the upper coupling surface of the cylinder block 19, a cylinder head cover 21 placed on the cylinder head 20 , and a crankcase 22 mounted on the lower coupling surface of the cylinder block 19 to accommodate a crankshaft 28. To the left side surface of the crankcase 22 is attached a generator crankcase 44 to accommodate a generator 42. The engine crankcase of this embodiment is formed by the crankcase 22 and the crankcase 44.

The rear surface of the cylinder head 20 is provided with an intake port 20b connected to a combustion recess 20a. The intake port 20b is connected through an intake pipe 23a to a carburetor 23. The front surface of the cylinder head 20 is provided with an exhaust port 20c connected to the combustion recess 20a. An exhaust pipe 24 is connected to the exhaust hole 20c. The exhaust pipe 24 extends obliquely towards the lower right side of the engine, along under the transmission case 45 (to be described later) and the right side of an overhanging portion of a lubricating oil chamber 22b, and obliquely to the rear, and is connected to a silencer 25 located to the right of the rear wheel 7. A spark plug 30 is inserted in the combustion recess 20a.

The cylinder block 19 has a chain chamber 19a formed on the left side and interconnecting the interior of the crankcase 22 and the interior of the cylinder head 20. A timing chain 34 placed in the chain chamber 19a moves a camshaft. 31 that moves to open and close an intake valve 32 and an exhaust valve 33 with the crankshaft 28.

In the cylinder hole of the cylinder block 19 a piston 26 is inserted for free sliding therein. The piston 26 is connected to the small end 27b of a connecting rod 27. The connecting rod 27, at its large end 27a, is connected to a wrist 29 mounted between right and left crank arms 28a and 28b.

A drive shaft 47 is positioned behind and parallel to the crankshaft 28. An output shaft 48 is coaxially positioned and to the left of the drive shaft 47. The output shaft 48, at its left end, is provided with a drive pinion 49 associated through a chain 50 with a driven pinion 51 on the rear wheel 7.

A generator 42 is mounted on the left end of the crankshaft 28. The generator 42 is constituted by a sleeve 43 keyed on the crankshaft 28, a rotor 42a fixed to the sleeve 43, and a stator 42b fixed, in a position radially opposite to the rotor 42a , to the generator housing 44.

The crankcase 22 is divided into the first crankcase 40 on the left side in the direction of the crankshaft and the second crankcase 41 on the right side. The generator housing 44 for housing the generator 42 is removably mounted on the outer side, in the direction of the crankshaft, of the first crankcase 40. The transmission case 45 used to house the CVT 16 is mounted on the outer side, on the crankshaft direction of the second crankcase 41.

The dividing line B of the first and second crankcases 40 and 41 is slightly offset to the left of the cylinder axis A. The first and second crankcases 40 and 41 are constituted, in general description, with first and second peripheral walls 40a and 41a which they generally open outward in the direction of the crankshaft, on whose inner side first and second support walls 40b and 41b are formed integrally supporting the crankshaft

28.

The first support wall 40b of the first crankcase 40 has a first crank support wall portion 40c to support, through a left stump support 35, the left crank stump portion 28c of the crankshaft 28, and a portion of Reducing gear mechanism support wall 40d formed by projecting a small amount to the left in the direction of the crankshaft relative to the first crank support wall portion 40c.

The second support wall 41b of the second crankcase 41 has a second crank support wall portion 41c for supporting the right crank stump portion 28d of the crankshaft 28 through a right stump support 36, and a wall portion of clutch support (clutch side support wall) 41d formed protruding beyond the cylinder axis A to the left in the direction of the crankshaft relative to the second crank support wall portion 41c.

The crank arms 28a, 28b, and the crank button 29 of the crankshaft 28 are housed in the crankshaft chamber 37 formed with the first and second crank support wall portions 40c and 41c.

The centrifugal clutch mechanism 17 is housed in a clutch chamber 38 formed with the second peripheral wall 41a and the clutch support wall portion 41d. The clutch chamber 38 is separated from the crankshaft chamber 37. In this embodiment, the wall portion that forms the clutch chamber 38 is called the clutch housing.

A reduction chamber 39 is formed with the reduction gear mechanism support wall portion 40d and the clutch support wall portion 41d to accommodate the reduction gear mechanism 18, and communicates with the crankshaft chamber 37.

The reduction gear mechanism 18 is constituted as follows: a reduction shaft 52 is placed parallel to the drive shaft 47 between the supporting wall portions 40d and 41d. The right side portion of the reduction shaft 52 is supported through a reduction shaft bearing 53 with the clutch support wall portion 41d while its left side portion is supported through a reduction shaft bearing 54 with a recess 40e formed in the support wall portion of reduction gear mechanism 40d. A small primary reduction gear 74 capable of relative rotation is mounted on the drive shaft 47 placed in the clutch chamber 38. A large primary reduction gear 75, which engages with the small primary reduction gear 74, is fixed with a key to the shaft reduction 52. The reduction axis 52 located in the reduction chamber 39 is integrally formed with a small secondary reduction gear 52a. A large secondary reduction gear 48a, which engages with the small secondary reduction gear 52a, is integrally formed with the output shaft 48.

The output shaft 48 is coaxially positioned with the drive shaft 47. The right end portion of the output shaft 48 is recessed with a support hole 48b into which the left end portion of the drive shaft 47 is to be inserted. The right end portion of the output shaft 48 is supported with the drive shaft 47 through a support 76 mounted in the support hole 48b. The left end portion of the output shaft 48 is passed through and is supported with the reducing gear mechanism support wall portion 40d of the first crankcase 40 through a support 77. The drive pinion 49 is fixed to the protruding end portion of the output shaft 48.

The CVT of the V-belt type 16 housed in the transmission case 45 includes a drive pulley and a driven pulley, its belt pitch diameters varying, around which a V-belt passes, the details of the constitution. They are the following.

The right outer end portion of the crankshaft 28, supported with the crankcase 22, protrudes in a cantilever shape to the transmission case 45, and a drive pulley 55 is mounted on the right outer end portion. The right outer end portion of the drive shaft 47, supported with the crankcase 22, projects as a cantilever to the drive case 45, and a driven pulley 56 is mounted on the right outer end portion. A V-belt 56 passes around the drive pulley 55 and the driven pulley 56.

The V-belt 57 is made of resin that is heat resistant and durable. The details of the constitution are as follows. Large number of resin blocks 57a, made of a material such as polyamide resin mixed with carbon fibers or aramid fibers and formed in a H-shaped side, are placed in succession and joined together using pairs of shaped connection elements 57b hoop made of highly heat resistant rubber. The right and left conical surfaces of the resin block 57a serve as contact surfaces for the drive pulley 55 and the driven pulley 56.

The drive pulley 55 is formed by a fixed pulley half 55a and a movable pulley half 55b, the first being fixed to the right end portion of the crankshaft 28 while the latter is placed on the inner side, in the direction of the crankshaft, of the fixed pulley half 55a, arranged so that it is axially sliding and rotating together with the crankshaft 28 through a sliding ring 59. An eccentric plate 58 and the sliding ring 59 are keyed on the right end portion of the crankshaft 28, on whose axially outer side half the fixed pulley 55a is mounted and fixed by means of a locking nut 60. Cylindrical ballasts 61 are placed between the movable pulley half 55b and the eccentric plate 58. When the crankshaft 28 rotates more rapidly, the ballasts 61 move radially outward by centrifugal force to move the movable pulley half 55b axially to the right and increase the direction radius of the pulley. As a result, the reduction ratio decreases.

The driven pulley 56 is formed by a fixed pulley half 56a and a movable pulley half 56b, the first one being fixed to the right outer end portion of the drive shaft 47 while the last one is placed on the outer side, in the direction of the crankshaft, of the fixed pulley half 56a, so that it is axially sliding. A cylindrical sliding ring 62 fixed to the axially central portion of the fixed pulley half 56a is keyed on the drive shaft 47. A cylindrical projecting member 63 fixed to the axially central portion of the movable pulley half 56b is mounted, so that it is axially sliding, on the sliding ring 62. Guide pins 64 mounted on the sliding ring 62 engage with sliding grooves 63a formed in the projecting member 63 so that the guide pins 64 can slide and the movable pulley half 56b can rotate together with the fixed pulley half 56a.

A spring receiving element 65 of an annular plate shape by means of a retaining ring 65a is mounted on the leading end portion of the sliding ring 62. A helical spring 67 for constantly pushing the movable pulley half 56b towards the fixed pulley half 56a is interposed between the spring receiving element 65 and the movable pulley half 56b.

The driven pulley 56 is pushed to a lowered position from the front end portion 62a of the slide ring 62 and is fixed to the drive shaft 47 by means of a locking nut 66 screwed into the front end 47a of the drive shaft 47.

Here, the inner diameter of the sliding ring 62 is staggered to a larger diameter than the outer diameter of the drive shaft 47, and the front end portion 47a of the drive shaft 47 is staggered to a smaller diameter. Thus, since the part of the drive shaft 47 for engaging with the lock nut 66 is made of smaller diameter, the lock nut 66 and the washer 66a are made of small diameter and can be gently placed in a position sunk into the sliding ring 62. In this way, it is possible to place the lock nut 66 in a lowered position in the direction of the crankshaft of the spring receiving element 65 for the helical spring 67.

The transmission case 45 is formed so that it is generally sealed and separated or independent of the crankcase 22 in an elliptical shape as seen from the right (Figure 4) in order to cover most of the right side of the crankcase 22. The Transmission case 45 is formed with two parts, a resin box 45a in the form of a bottom box that opens to the outer side in the direction of the crankshaft, and an aluminum cover 45b that closes the hole in an airtight state.

The box 45a and the cover 45b are fixed, using the protruding portions 45e and 45d formed on the peripheral edges of the components and bolts 70, to the second crankcase 41. The box 45a has been formed with protruding portions 45i and 45i coaxially with the crankshaft 28 and the drive shaft 47 and is mounted on the protruding portions that support the outer bearings of the bearings 36 and 81 on the crankcase side. In this way, the box 45a is arranged so that it is supported on the side of the crankcase even in the state in which the bolts 70 are removed.

A space (a) has been formed between the bottom wall 45c of the case 45a and the second crankcase 41. The space (a) prevents heat from the engine 2 from being transmitted through the crankcase 22 to the transmission case 45 and prevents the temperature increase in the transmission case 45 allowing the flow of air produced between both boxes when the vehicle is traveling.

The lower portion 22a of the crankcase 22 has been formed with a lubricating oil chamber 95 having an overhanging portion formed integrally 22b which bulges towards the lower side of the transmission case 45 (see Figures 8 and 11). As a result of providing the lubricating oil chamber 95 with the protruding portion 22b, the center line (D) of the lubricating oil chamber 95 as a whole, including the protruding portion 22b, moves from the centerline to the width of the engine ( cylinder shaft line A) to the transmission case 45. The inner wall 22c of the lubricating oil chamber 95, in front of the transmission case 45, is in the same position, in the direction of the crankshaft, as the support wall 40c to support the left stump support 35.

The projecting portion 22b has been formed, as seen in plan view, so that it is within the projecting area of ​​the transmission case 45. A space (b) is provided between the upper surface of the projecting portion 22b and the underside of the transmission case 45. The exhaust pipe 24 is arranged so that it passes through the area that is within the projection in plan view of the transmission case 45 and within the projection in side view of the projecting portion 22b.

According to the present embodiment, the crankshaft 28 and the transmission shaft 47 are rotatably supported with the crankcase 22 and their right outer ends are made to project overhanging the transmission case 45 in a constitution such that the distal ends of the crankshaft 28 and the drive shaft 47 does not require stump support. As a result, no support portion is required in the transmission case 45 in particular on the side of the cover 45b, and consequently the transmission case 45 as a whole may be of reduced size and weight.

Together with the cantilever constitution of the crankshaft 28 and the transmission shaft 47 as described above, the constitution to support the transmission case 45 with the crankcase 22 does not therefore require greater rigidity, so that the constitution can be simplified of support. In other words, if the front end of the crankshaft 28 and the like are supported on a stump, the transmission case 47 itself would have to be done with a high rigidity and connected to the crankcase 22 with a high rigidity to ensure the exact positioning of the support.

Since the space (a) has been arranged between the transmission case 45 and the crankcase 22, it is unlikely that the heat of the engine is transmitted from the crankcase side to the transmission case 45. In addition, the transmission case 45 is cools and prevents its temperature from rising with the flow of air through the space (a) when the vehicle is traveling, resulting in improved durability of the V-belt 57. In addition, since the transmission case 45 can be of reduced size and weight as described above, the area around the CVT 16 of the engine is prevented from being large even if the space (a) is provided.

Since the box 45a, which serves as a crankcase side surface facing the crankcase 22, of the transmission case 45 is made of a resin element, the transmission box 45 is of smaller size and weight and the durability of the V-belt 57 because the temperature increase in the transmission case 45 is avoided. That is, the use of the resin element increases the freedom of formation and therefore it is easy to form the transmission case 45 of a small size . Since the resin elements have a higher thermal insulation property than the aluminum alloy elements commonly used for crankcase elements, increasing the temperature in the transmission case 45 is more reliably avoided by further reducing heat transmission. .

Since the V-belt 57 is made as a resin belt by joining together the resin blocks 57a by means of the connecting elements 57b, the heat generated with the V-belt is limited, that is, the resin belt with the portion in contact with the drive pulley 55 made of a resin element can produce the same transmission torque with a lower compression force of the drive pulley 55 compared, for example, with a rubber belt. Accordingly, the heat generated by friction between the V-belt 57 and the drive pulley 55 is reduced, so that the temperature increase of the belt is reduced.

As described above, it is possible to avoid the temperature increase of the transmission case 45, prevent the heat produced by friction by making the V-belt with a resin element, and improve the heat resistance and durability of the belt in comparison with a rubber strap, so that the V-belt 57 does not require refrigeration. As a result, the transmission case 45 can be made in a sealed constitution to prevent water and dust from entering.

Since the lower portion 22a of the crankcase 22 has been formed with the projecting portion 22b projecting towards the lower side of the transmission case 45, the clearance below the transmission case 45 is effectively used to increase the amount of lubricating oil in the lubricating oil chamber 95. Therefore, unlike the arrangement in which the depth of the lower part of the crankcase is increased to ensure the amount of lubricating oil, the height of the engine 2 must not be increased.

Since the lower portion 22a of the crankcase 22 bulges towards the lower side of the transmission case 45, the surface area of ​​the lubricating oil chamber 95 is increased, whereby the cooling property is consequently improved and the balance is improved engine weight together. Since the space (b) is disposed between the projecting portion 22b and the transmission case 45, it is prevented that the heat of the lubricating oil in the projecting portion 22b is transmitted to the transmission case 45, and the transmission case 45 is cooled with the flow of air that takes place and circulates through the space (b) when the vehicle is traveling.

Here, since this embodiment is arranged so that the V-belt is made of a resin element and the transmission case 45 is made so that it is independent of the crankcase 22, the heat resistance and durability of the belt in V are improved compared to an arrangement using a rubber belt, and the thermal effect of the motor is avoided. As a result, it is possible to reduce the diameters of the drive pulley 55 and the driven pulley 56, and the size of the transmission case 45. This makes it possible to produce a clearance below the transmission case 45 and consequently form the protruding portion , increase the capacity of lubricating oil, and ensure the space to place the exhaust pipe 24.

Since this embodiment is arranged so that the movable pulley half 56b of the driven pulley 56 mounted on the drive shaft 47 is located on the outer side in the direction of the crankshaft of the fixed pulley half 56a, it is possible to ensure a clearance on the inner side of the driven pulley 56 of the drive shaft 47 and use the space to place the centrifugal clutch mechanism 17 adjacent to the fixed pulley half 56a. This makes it possible to coaxially position the output shaft 48 on a part of the drive shaft 47 located on the opposite side of the driven pulley 56 without increasing the width of the motor. As a result, unlike the conventional arrangement of placing the output shaft behind the drive shaft, the engine size can be reduced in the longitudinal direction of the vehicle.

Since this embodiment is arranged so that the locking nut 66 is placed in an axially lowered position using the spring receiving element 65 that supports the helical spring 67 to push the movable pulley half 56b against the fixed pulley half 56a , it is possible to avoid increasing the size of the engine in the vehicle width direction by reducing the amount of projection of the coil spring 67 towards the outer side in the direction of the transmission shaft with a simple constitution, while ensuring the necessary length of the coil spring 67.

In other words, in a constitution represented, for example, in Figure 16 in which a sliding ring 201 is fixed to a drive shaft 200 by tightening a locking nut 203 on the outer end surface of the sliding ring 201, a box Transmission 204 protrudes outward in the width-wide direction of the vehicle according to the size of the lock nut 203. In contrast to the above, this embodiment is arranged so that the locking nut 66 is placed in an axially lowered position from the outer end of the spring receiving element 65, so that the projection of the transmission case 45 is reduced one dimension (t), approximately 10 mm.

Since the coil spring 67 is located on the axially outer side, service of the coil spring 67 can be easily performed after only removing the retaining ring 65a. If the movable pulley half was placed inside the fixed pulley half, or if the helical spring were placed axially on the inner side, the efficiency of the maintenance operation would be poor because all the pulley moved would have to be removed.

On the outer side in the direction of the crankshaft of the second peripheral wall 41a forming the clutch chamber 38, a hole 41e of the size has been formed which allows the centrifugal clutch mechanism to be introduced and removed.

17. A clutch cover 71 (wall to support the other side of the clutch) is mounted in a hermetic state in the hole 41e. The clutch cover 71 is removably fixed to the hole edge of the second peripheral wall 41a by means of bolts 72. In this way, the transmission case 45 can be removed together with the driven pulley 56, and the centrifugal clutch mechanism 17 can be removed together with the drive shaft 47 after removing the clutch cover 71.

The centrifugal clutch mechanism 17 is positioned and supported so that it is axially motionless with clutch bearings 80 on one side and 81 on the other side, the first one being mounted on the axially left end and the last one in the center of the transmission shaft 47 The clutch bearing 80 on one side is supported with the clutch support wall portion 41d. Clutch bearing 81 on the other side is supported with clutch cover 71.

The clutch support wall portion 41d that supports the clutch bearing 80 and the reduction shaft bearing 53 is offset to the left of the second crank support wall portion 41c that supports the right stump support 36. In In other words, it is located between the first crank support wall portion 40c that supports the left stump support 35 and the second crank support wall portion 41c. To put it more specifically, it is located on the cylinder axis A or slightly displaced from the cylinder axis A towards the dividing line B. The clutch cover 71 that supports the clutch bearing 81 on the other side is located more on the side right outside in the direction of the crankshaft that the second crank support wall portion 41b supporting the right stump support 36. The reducing gear mechanism support wall portion 40d supporting the left support 77 of the output shaft 48 is located more on the left outer side than the first crank support wall portion 40c that supports the left stump support 35 .

The crankcase 22 is divided in the direction of the crankshaft into the first and second crankcases 40 and 41. The transmission case 45 is placed on the outer side in the direction of the crankshaft of the second crankcase 41. The centrifugal clutch mechanism 17 is located near on the inner side in the direction of the crankshaft of the transmission case

Four. Five. As a result, it is possible to position the output shaft 48 coaxially with the drive shaft 47 on the opposite side of the CVT 16 to reduce the longitudinal dimension of the motor 2 while restricting its width dimension.

Since the centrifugal clutch mechanism 17 is supported at two points with one and the other clutch bearings 80 and 81, the centrifugal clutch mechanism 17 is placed in the axial direction and is supported with a simple constitution without using separate components.

This embodiment is arranged so that the clutch support wall portion 41d that supports the clutch bearing 80 on one side is positioned between the first and second crank support wall portions 40c and 41c that support the left and right bearings 35 and 36 of crankshaft 28, and the clutch cover 71 (wall to support the other side of the clutch) that supports the clutch bearing 81 on the other side is located on the outer side in the direction of the crankshaft of the second crank support wall portion 41c which supports the right stump support 36. Therefore, it is possible to ensure the capacity of the clutch chamber 38 while reducing the wheelbase of the crankshaft 28 and the drive shaft 47 compared to an arrangement in which the first crank support wall 40c and the Clutch support wall 41 on one side are located on the same line, and the second crank support wall 41c and clutch cover 71 are located on the same line, so that the centrifugal clutch mechanism 17 is housed compactly and the motor as a whole is compact.

Since the clutch cover 71 is removably mounted in the hole 41e of the second crankcase 41, the maintenance and replacement of parts can be done easily because the centrifugal clutch 17 can be removed together with the drive shaft 47 after removing the transmission case 45 and clutch cover 71.

In this embodiment, the output shaft 48 is coaxially located on the side, opposite the transmission case 45, of the drive shaft 47, and the drive pinion 49 is mounted on the output shaft 48. Because of this, it is It is possible to coaxially position the centrifugal clutch mechanism 17 and the drive pinion 49 to reduce the size of the engine in the longitudinal direction of the vehicle.

The centrifugal clutch mechanism 17 is located near the inner side in the direction of the crankshaft of the driven pulley 56. The centrifugal clutch mechanism 17 is of the wet multi-layer type, as represented mainly in Figures 12 to 15, constituted in general description as follows: the projection 83b of a cup-like outer clutch 83 is keyed on the drive shaft 47 to rotate together. An inner clutch 84 is coaxially positioned on the axially inner side of the outer clutch 83. The hub portion 84a of the inner clutch 84 is keyed on the small primary reduction gear 74 to rotate together. By the way, the small primary reduction gear 74 is rotatably mounted on the drive shaft 47.

Multiple outer clutch plates 85 are placed on the outer clutch 83 and on their two sides two pressure plates 86 and 86 are placed. Components 85 and 86 are engaged with the outer clutch 83 so that they rotate together. Inner clutch plates 87 are positioned between the outer clutch plates 85 and the pressure plates 86. The inner clutch plates 87 are engaged with the outer periphery of the inner clutch 84 so that they rotate together.

An eccentric surface 83a has been formed inside the outer clutch 83 and weights 88 are placed between the eccentric surface 83a and the pressure plates 86 located on the outer side. When the centrifugal force acts on the ballasts 88, they are moved to the left and radially outward of the outer clutch 83 in Figure 12 (in the direction of clutch engagement) to press and move the pressure plates 86 and make the plates of outer and inner clutch 85 and 86 engage with each other. By the way, the upper half of Figure 12 represents the centrifugal clutch mechanism 17 in the disengaged state and the lower half represents the engaged state.

The centrifugal clutch mechanism 17 is provided with an anti-slip mechanism of clutch plate 90. The anti-slip mechanism of clutch plate 90 is formed by sheet springs 91 interposed between the outer clutch plates 85, and between the clutch plates outer 85 and the pressure plates 86 to push the outer clutch plates 85 and the pressure plates 86 in the direction of mutual separation.

To prevent the inner clutch plates 87 from moving in the axial direction, pins 92 are passed through the inner clutch plates 87 at circumferential intervals. Helical springs 93 have been placed between the inner clutch plates 87 to push them in the direction of mutual separation.

In the centrifugal clutch mechanism 17 of this embodiment, the ballasts 88 move radially outward by centrifugal force when the motor revolution increases, and their axial positions are determined with the eccentric surface 83a. When the engine revolution exceeds a predetermined value by the throttle opening operation (not shown), the ballasts 88 press and move the pressure plates 86, and jointly press the outer and inner clutch plates 85 and 87. Then the The engine revolution is transmitted from the drive shaft 47 through the gear reduction mechanism 18 to the output shaft 48. The rotation of the output shaft 48 causes the rear wheel 7 to rotate through the drive pinion 49 and the chain

50.

When the choke closes and the engine revolution decreases, the ballasts 88 move radially inwards. When the engine revolution falls below a predetermined value, the pressure force of the ballasts 88 is released, the outer and inner clutch plates 85 and 87 perform a relative rotation, and the engine revolution is disengaged between the shaft of transmission 47 and output shaft 48.

When the clutch disengages and the pressure force is released, the outer clutch plates 85 and the pressure plates 86 separate from each other with the repulsive force of the sheet springs 91, and the inner clutch plates 87 are they separate one from the other with the repulsive force of the coil springs 93.

This prevents the outer and inner clutch plates 85 and 87 from adhering to each other due to the lubricating oil and preventing the clutch from being dragged.

Since the pins 92 prevent the inner clutch plates 87 from moving in the axial direction, the inner clutch plates 87 are prevented from tipping when the clutch disengages, which also helps prevent clutch dragging.

Next, the lubricating oil system of engine 2 will be described.

The lubricating oil system is arranged so that the lubricating oil in the lubricating oil chamber 95 formed in the lower portion 22a of the crankcase 22 is sucked up and fed under pressure with an oil pump 96 to the crankshaft bearings 28, the camshaft 31, and other sliding parts to be lubricated, and can freely fall and return to the lubricating oil chamber 95.

The oil pump 96, as depicted primarily in Figure 11, is placed at the bottom of the first crankcase 40 of the crankcase 22 and includes a pump shaft 96a supported with a housing 97 having a suction hole 97a and a hole discharge 97b, and a pump gear 98 mounted on the outer end portion of the pump shaft 96a.

A suction passage 40f communicating with the suction hole 97a is formed in the first crankcase 40 and is opened through an oil artichoke 99 on the bottom surface in the lubricating oil chamber 95. A lubricating oil supply passage 40g communicating with the discharge orifice 97b is also formed in the first crankcase 40 and is communicated through an oil filter 100 with a main supply passage 44a formed in the generator crankcase 44. The downward end of the main supply passage 44a is connected to an oil chamber 44c that communicates with the left end surface of the crankshaft 28.

An oil passage 28e communicating with the oil chamber 44c is axially formed in the crankshaft 28 and is opened, through a bifurcation passage 29a formed in the wrist 29, to a connection support portion 101 where the wrist 29 and connecting rod 27 are interconnected.

The lubricating oil sucked with the oil pump 96 is fed under pressure through the supply passage 40g and the main supply passage 44a to the oil passage 28e and then through the bifurcation passage 29a to the support connection portion 101 The lubricating oil supplied to the support connection portion 101 spreads with the oil feed pressure and the centrifugal force of the crankshaft 28 inside the crankshaft chamber 37. Some of the scattered lubricating oil enters the reduction chamber 39 to lubricate the small secondary reduction gear 52a and the large secondary reduction gear 48a and falls into the lubricating oil chamber 95.

The lubrication constitution of the centrifugal clutch mechanism 17 will be described below.

As shown in Figures 3 and 7, part of the centrifugal clutch mechanism 17 is located in the area, as seen in the direction at right angles to the crankshaft, where the lubricating oil is spread from the support connection portion 101 of the connecting rod 27 and the wrist 29. That is, the outer and inner clutch plates 85 and 87 of the centrifugal clutch mechanism 17 are located facing the crankshaft chamber 37.

An inlet hole 103 for directing the spread lubricating oil from the support connection portion 101 to the clutch chamber 38 is formed in the second peripheral wall 41a defining the crankshaft chamber 37 and the clutch chamber 38.

The clutch support wall portion 41d is integrally formed with a guide portion 104 that extends into the interior of the clutch chamber 38. The guide portion 104 is located at the extension of the line that interconnects the crankshaft 28 and the drive shaft 47 and includes a receiving portion of lubricating oil 104a that extends vertically so that it generally looks at the inlet hole 103 and a guide portion 104b which extends continuously and arched from the lower end of the receiving portion of lubricating oil 104a to the lower side of the transmission shaft 47. The guide portion 104b is located inserted in the protruding cone-shaped portion of the inner clutch 84.

With the above arrangement, the lubricating oil entering through the inlet hole 103 is received with the guide portion 104, guided more to the inner side than to the outer side of the centrifugal clutch mechanism 17, supplied by the centrifugal force of the mechanism centrifugal clutch 17 between outer and inner clutch plates 85 and 87, and supplied to the hitch zone of the large and small primary reduction gears 75 and 74 (as shown with arrows in Figures 3 and 7).

The lubrication structure of the centrifugal clutch mechanism of the present embodiment is arranged such that the lubricating oil supplied to the support connection portion 101 of the wrist 29 and the large end of the connecting rod 27a is directed to the centrifugal clutch mechanism 17. Therefore, it is possible to supply a large amount of lubricating oil that spreads from the support connection portion 101 to the centrifugal clutch mechanism 17 preventing the outer and inner clutch plates 85 and 87 from being seized by heat without using a special passage of lubricating oil.

This embodiment makes it possible to effectively direct the lubricating oil from the crankshaft chamber 37 to the clutch chamber 38 with a very simple constitution since the centrifugal clutch mechanism 17 is located, as seen in the direction at right angles to the crankshaft, in the area over which the lubricating oil is spread from the support connection portion 101, and the inlet hole 103 to allow the entry of lubricating oil is formed in the second peripheral wall 41a defining the clutch chamber 38 and the crankshaft chamber 37.

This embodiment is arranged so that the clutch support wall portion 41d is integrally formed with a guide portion 104 that extends into the interior of the clutch chamber 38. The guide portion 104 is located at the extension of the line that interconnects the crankshaft 28 and the drive shaft 47 and includes a receiving portion of lubricating oil 104a that extends vertically so that it generally looks at the inlet hole 103 and a guide portion 104b which extends continuously and arched from the lower end of the receiving portion of lubricating oil 104a to the lower side of the transmission shaft 47. Therefore, the lubricating oil is more safely supplied to the outer and inner clutch plates 85 and 87.

Next, the engine start mechanism 2 will be described.

As shown mainly in Figures 5, 9, and 10, a starter shaft 110 is placed parallel and almost vertically below the output shaft 48. The starter shaft 110, as seen at right angles to the direction of the crankshaft, it is supported on the portion inside the drive pinion 49 with the protruding portion 40h of the first crankcase 40 and on the outer portion with the protruding portion 44b formed integrally with the generator cover 44.

A starter arm 111 is mounted on the outer end of the starter shaft 110. A starter gear 112 is keyed, so that it is axially sliding, on the inner end portion of the starter shaft 110 and is located within the first crankcase. 40. A return spring 113 is wound around the inner end portion of the starter shaft 110 to push the starter shaft 110 into the initial position.

A main intermediate shaft 114 and a secondary intermediate shaft 115 are positioned between the starter shaft 110 and the crankshaft 28 and parallel to the starter shaft 110. The main intermediate shaft 114 extends between the first and second crankcases 40 and 41 and is supported. articulated with them. An intermediate main gear 116 capable of engaging with the starter gear 112 is mounted on the main intermediate shaft 114.

The secondary intermediate shaft 115 is supported with the support portion 40 formed in the first crankcase 40. The inner and outer ends of the secondary intermediate shaft 115 respectively protrude in and out of the first crankcase 40. A first intermediate gear 115a to engage with the intermediate main gear 116 is integrally formed within the crankcase of the secondary intermediate shaft 115 and a second intermediate gear 117 is attached outside the crankcase. The second intermediate gear 117 engages with a first crank gear 121 which will be described later.

As the starter arm 111 is pushed down, the starter shaft 110 rotates, the starter gear 112 moves axially and engages with the intermediate main gear 116 to transmit the rotation to the first crank gear 121 through the intermediate gears first and second 115a and 117 and turn the crankshaft

28.

A part of the crankshaft 28 between the left stump support 35 and the sleeve 43 of the generator 42 is provided with a unidirectional clutch 120, the first crank gear 121, and an eccentric pinion 122 in order from the outer side.

The unidirectional clutch 120 is provided with a starter gear 120a connected through a crazy gear 124 to a drive gear 125a of a starter motor 125. The starter motor 125, with its drive shaft parallel to the crankshaft 28, is fixed to the front wall of the crankcase 22.

The starter gear 112, the intermediate main gear 116, and the first intermediate gear 115a are located in a position that communicates with the lubricating oil chamber 95 within the first crankcase 40. The second intermediate gear 117, the first crank gear 121 , and the eccentric pinion 122 are located outside the first crankcase 40.

Since the starter mechanism of this embodiment is arranged so that the starter gear 112, the intermediate main gear 116, and the first intermediate gear 115a are located in the position that communicates with the lubricating oil chamber 95, the parts of Engagement of said gears are sufficiently lubricated.

Since the secondary intermediate shaft 115 is passed through the first crankcase 40 from the inside to the outside to transmit the rotation of the starter shaft 110 from the inner side of the secondary intermediate shaft 115 to the outer side, and from the second intermediate gear 117 on the outer side of the crankshaft 28 through the first crank gear 121, it is possible to place the first crank gear 121 on the outermost side than the crank stump portion 28c, to reduce the distance between the crankshaft bearings 35 and 36, and to support the crank shaft 28 while reducing the bending moment due to the connecting rod 27. It is also possible to secure the arrangement space for the eccentric pinion 122 and the second crank gear 127 in order to facilitate the arrangement around the crankshaft. In other words, if the rotation of the starter shaft 110 was made to be transmitted to the crankshaft 28 within the first crankcase 40, a gear would be required between the left crankshaft bearing 35 and the left crank arm 28a, the distance between the bearings. Left and right 35 and 36 would increase by missing the bending moment mentioned above.

Since this embodiment is arranged so that the starter shaft 110 is located almost vertically below the output shaft 48, the starter arm 111 is easy to push down and the size of the motor 2 can be reduced in the longitudinal direction of the vehicle.

Part of the starter shaft 110 on the inner side in the vehicle width direction of the rear wheel drive sprocket 49 is supported with the first clutch support wall portion 40d, part of it on the outer side in the direction the width of the vehicle is supported with the generator housing 44, and the starter arm 111 is mounted on a part of the starter shaft 111 that protrudes outside the starter shaft 110 more than the generator case 44. Therefore, it is possible to place the starter shaft 110 and the starter arm 111 in optimal positions for downward thrust without interfering with the rear wheel drive sprocket 49.

As shown in Figure 4, the starter shaft 110, as seen in the direction of the crankshaft, is located within the axial projection zone of the transmission case 45 and within the axial projection zone of the clutch mechanism centrifuge 17. That is, it is located almost just below the driven pulley 56.

Since the starter shaft 110 is positioned on the opposite side of the transmission case 45 as described above, there is no need to secure a space to place the starter shaft in the transmission case 45, so that it is possible to place the drive pulley 55 and the driven pulley 56 of the CVT 16 close to each other to the extent that there is only a small interval (b ') (see Figure 3) and consequently the dimension is reduced of the engine 2 in the longitudinal direction of the vehicle.

Since the starter shaft 110 is positioned within the projection zone in the direction of the crankcase crank 45, it is possible to place the starter shaft 110 in a position that is close to the crankshaft 28 and is easy to push down.

Since this embodiment is arranged so that the centrifugal clutch mechanism 17 is placed close on the inner side in the direction of the crankshaft of the driven pulley 56, and since the starter shaft 110 is placed in a position that is within the axial projection zone of the centrifugal clutch mechanism 17 and almost vertically below the drive shaft 47, it is possible to use a free space within the projection zone of the centrifugal clutch mechanism to place the starter shaft 110 in the optimum position for the downward thrust and to reduce the size of the motor 2 in the longitudinal direction of the vehicle.

A balancer shaft 129 is placed parallel and backward on the crankshaft 28. The balancer shaft 129 is supported through balancer shaft bearings 130 and 131 with the first and second crankcases 40 and 41. The left end of the balancer shaft 129 protrudes outside the first crankcase 40 and is connected to a balancer gear 132. A damping element 133 is mounted on the inner circumferential surface of the balancer gear 132.

Here, the left and right crank arms 28a and 28b of the crankshaft 28 are located within the balancer bearings 130 and 131, and the balancer ballast 129a of the balancer shaft 129 is positioned between the left and right crank arms 28a and 28b and near the crankshaft 28 so that it is superimposed on the rotating place of the wrist 29. This makes the area around the balance shaft compact.

The crankshaft 28 is snapped into the first crank gear (first drive gear) 121 to which a second crank gear (second drive gear) 127 is attached to rotate together. The balancer gear (second gear moved) 132 engages with the second crank gear 127. That is, inner circumferential teeth 127a are formed on the inner circumferential surface of the second crank gear 127, engaging the inner circumferential teeth with the outer circumferential teeth 121a of the first crank gear 121 (see Figure 6). In this way, the rotation of the crankshaft 28 is transmitted from the first crank gear 121 through the second crank gear 127 to the balancer gear 132.

the pump gear (first gear moved) 98 is connected through the second intermediate gear 117 to the first crank gear 121. In this way, the first crank gear 121 and the second intermediate gear 117 are used for both start and drive of the oil pump.

The unidirectional clutch 120, the first crank gear 121, and the eccentric pinion 122 mounted to the crankshaft 28 are held so that they are axially motionless between the sleeve 43 and the stump support 35 when a nut 123 is screwed and tightened on the left end portion of the crankshaft 28.

This embodiment is arranged so that the second intermediate gear 117 that engages with the first crank gear 121 is used both to transmit the rotation of the starter shaft 110 to the crankshaft 28 and to transmit the rotation of the crankshaft 28 to the gear pump 98 , so that it is possible to reduce the length of the crankshaft accordingly and make the engine of compact width.

This embodiment is also arranged so that the crankshaft 28 snaps into the first crank gear 121 that engages both the inner circumferential teeth 127a of the second crank gear 127 and the second intermediate gear 117. Therefore, the length of part of the first crank gear 121 snapped onto the crankshaft 28 can be long enough to reliably transmit the rotation of the crankshaft 28 to the pump gear 98 and the balancer gear 132.

This embodiment is arranged so that the outer circumferential teeth 121a of the first crank gear 121 engage with the inner circumferential teeth 127a of the second crank gear 127. Therefore, it is easy to install the second crank gear 127 and remove it for maintenance. That is, the second crank gear 127 can be easily removed from the first crank gear 121 after removing the nut 123 of the crankshaft 28 and removing the sleeve 43 and the unidirectional clutch 121.

The multi-axis placement arrangement of the motor 2 is as follows.

As seen in the direction of the crankshaft, the drive shaft 47 and the output shaft 48 are behind and at the same level as the crankshaft 28. The balancer shaft 129 and the reduction shaft 52 are positioned above the plane C that includes the crankshaft shafts 28 and output shaft 48. The starter shaft 110, the pump shaft 96a, and the main and secondary intermediate shafts 114 and 115 are positioned above the C plane.

The starter shaft 110 is positioned almost vertically below the output shaft 48. The pump shaft 96a is positioned almost vertically below the balancer shaft 129. The main and secondary intermediate shafts 114, 115 are placed in the line that interconnects the crankshaft 28 and starter shaft 110.

This embodiment is arranged so that the balancer shaft 129 is positioned above the plane C which includes the crankshaft axes 28 and the output shaft 48, and the starter shaft 110 and the pump shaft 96a of the oil pump 96 are below the C plane, so that these components are well balanced in upper and lower positions to avoid increasing the size of the engine. That is, there is a clearance behind the cylinder hole and above the plane C, and the space is used to position the balancing shaft 129. Since the balancing shaft 129 rotates with a large rotation place of the ballast 129a, if the ballast submerged in lubricating oil, a lot of power would be lost when the lubricating oil was agitated. With this embodiment, however, the balancing shaft 129 does not agitate lubricating oil. This embodiment is also arranged so that the reduction axis 52 is positioned using the clearance above the plane C and between the balancing axis 129 and the output axis 48. Although the reduction shaft 52 is placed in a high position at which lubricating oil is less likely to spread, since the lubricated oil scattered from the support connecting portion 101 of the crankshaft rod 28 is supplied to the reduction gear 75 and other parts, there is no problem regarding poor lubrication.

Since the starter shaft 110 is placed almost vertically below the output shaft 48, it is possible to reduce the longitudinal size of the motor 2 and place the starter shaft 110 in a position where it is easy to push it down.

Figures 17 to 19 are intended to explain the second embodiment of the invention. In the drawings, the same reference numbers as those in Figures 1 to 15 denote identical or equivalent parts. This embodiment is an example intended for air cooling the transmission case 45.

The transmission box 45 is provided with an inlet 45e to introduce air and outlets 45f and 45g to discharge air out. The inlet 45e has been formed in the aluminum alloy cover 45b in alignment with the axis of the drive pulley 55. The downward end hole of an air inlet duct 45h fits in the inlet 45e. The air introduction duct 45h is fixed to the cap 45b with bolts and extends towards the front of the vehicle.

Exits 45f and 45g are formed in the resin box 45a and open to the space (a) between the transmission box 45 and the crankcase 22. The outlets 45f and 45g are also formed so that they are placed in the area above the line E that interconnects the crankshaft 28 and the drive shaft 47, namely, so that the bottom edges of the outlets 45f and 45g are located above the line E and between the crankshaft introduction hole 28 'and the transmission shaft introduction hole 47'.

A wall 100 has been formed along the periphery of the transmission case 45 so that it surrounds the space

(a) between the transmission case 45 and the crankcase 22. The wall 100 has been formed in the shaded area in Figure 19. A hole 100c has been formed in the lower zone (not shaded) and opens the space (a ) to the external space.

The wall 100 is formed by an engine side wall portion 100a formed on the side of the crankcase 22 and a transmission wall portion 100b formed on the side of the resin case 45a, looking at both wall portions and being in contact with one with other.

The hole 100c is located above the projecting portion 22b of the lubricating oil chamber 95 and communicates with the outer space through the space (b) between the projecting portion 22b and the transmission case 45.

The second embodiment is arranged so that the transmission case 45 is provided with the inlet 45e for introducing air and with the outlets 45f and 45g for discharging air outward, so that air is introduced into the transmission case 45 to cool positively box. In addition, since the outlets 45f and 45g open to the space (a) between the transmission case 45 and the crankcase 22, the heat stagnant in the space (a) can be expelled when air is discharged, and the air discharge also prevents heat from being transmitted on the crankcase side.

Since the outputs 45f and 45g are located above the line E that interconnects the crankshaft and the transmission shaft, rainwater or the like is prevented from entering the transmission case 45.

Since the outlets 45f and 45g are formed so that they are located on the rear sides of the drive pulley 55 and the driven pulley 56 of the transmission case 45, it is possible to cause air to flow along the rear sides of the pulleys where heat is likely to stagnate and more reliably prevent the temperature in the transmission case from rising 45.

Since the wall 100 has been formed by covering the space (a) between the transmission case 45 and the crankcase 22 above and the bottom of the wall 100 is provided with the hole 100c, it is reliably prevented from entering rainwater or the like in the discharge holes 45f and 45g through the space (a) between the transmission case 45 and the crankcase

22.

Since part of the wall 100 is integrally formed with the box 45a with a resin element, heat is prevented from being transmitted on the crankcase side through the wall 100.

By the way, it is possible to arrange the first embodiment (shown in Figures 1 to 15) with the air introduction hole 45e and the outlets 45f, 45g as the second embodiment (represented in Figures 17 to 18). In that case, the temperature increase in the transmission case 45 is more reliably prevented.

According to one embodiment, the V-belt is a resin belt that joins a large number of blocks, part of each block being in contact with the drive pulley and the driven pulley made of a resin element. Therefore, it is prevented from generating heat generated with the V-belt itself. That is, the resin belt with the portion in contact with the drive pulley made of a resin element can produce the same transmission torque with a lower compression force of the drive pulley compared, for example, with a belt. of rubber. Consequently, the heat generated by friction between the V-belt and the drive pulley is reduced, and the temperature increase of the belt itself is avoided.

Since at least part of the transmission case supported with the engine case is made of a resin element, the amount of heat transmitted from the engine side case through the support portion to the side of the transmission case It is reduced with greater certainty.

According to one embodiment, the transmission case is of a generally sealed constitution; It perfectly prevents rainwater, mud, and the like from entering the transmission case. Since it is also envisioned that the V belt is a resin belt made by joining together a large number of blocks, part of each block being in contact with the drive pulley and the driven pulley made of a resin element, the heat produced by friction between the belt and pulley compared to an arrangement using a rubber belt, and the increase in internal temperature is avoided despite the sealed constitution of the transmission case.

According to one embodiment, the lubricating oil chamber formed with the engine housing is bulged outwardly under the transmission case so that there is a gap between it and the transmission case. As a result, it is possible to prevent the overall size, especially the height, of the engine from increasing and prevent the temperature of the transmission case from increasing while ensuring the necessary lubricating oil chamber capacity. In other words, if the lower part of the engine housing were swung down to ensure a sufficient amount of lubricating oil, the overall height of the engine would increase. The inventor of this invention has noted the presence of a relatively large unused space under the transmission case placed on the side of the engine crankcase, and has caused the lubricating oil chamber to bulge into space. As a result, the capacity of the lubricating oil chamber is ensured without increasing the overall height of the engine. Since a space is between the protruding portion and the transmission case, it is possible to prevent the transmission of heat from lubricating oil to the transmission case and to cool the transmission case itself with the air flow taking place through the space when the vehicle is traveling

According to one embodiment, the outputs are located between the crankshaft introduction hole and the transmission shaft input hole of the transmission case, so that the outputs are generally located behind the V-belt part between the pulleys drive and driven or behind the drive and driven pulleys. Therefore, it is possible to cause the air introduced into the transmission case to collide in the V-belt or to flow along the rear side of the pulley where heat is likely to stagnate, to cool the V-belt directly, and safely avoid increasing the temperature in the transmission case.

According to one embodiment, at least part of the transmission case that looks at the engine housing is made of a resin element. Therefore, it is possible to further reduce the size of the transmission case and improve the durability of the V-belt by preventing the temperature increase of the transmission case. That is, the use of the resin element increases the degree of freedom of the shape, and the transmission case can be made of a smaller size. Since the resin element transmits less heat compared to the aluminum alloy or the like, the material commonly used for the case, the temperature increase in the transmission case is more reliably avoided.

According to one embodiment, the movable pulley half of the driven pulley mounted on the drive shaft is located on the outer side in the direction of the crankshaft of the fixed pulley half and the centrifugal clutch mechanism is installed adjacent to the pulley half fixed and in the direction of the crankshaft. Therefore, it is possible to secure a space on the inner side of the driven pulley of the drive shaft and use the space to position the centrifugal clutch mechanism. This makes it possible to coaxially position the output shaft on the opposite side of the driven pulley of the drive shaft. As a result, the longitudinal size of the engine can be reduced without increasing the width of the engine.